Conventionally, in order to acquire a distribution of deformation shapes on a circumference of a rotating tire at a tread portion, or to acquire a contact length of a rotating tire, finite element models have been used to simulate rotating tires. In such acquiring method, it has been difficult to acquire the deformation shape at the tread portion or the contact length within a short period of time, because of the time required for creating a finite element model or for simulation calculation. Therefore, a contact length (dynamic contact length) and a deformation shape obtained with a non-rotating tire have been used in place of the contact length and the tire deformation shape of the rotating tire.
However, for estimating tire performance, it has been demanded to acquire the contact length and the deformation shape by measuring the rotating tire, since the contact length and the deformation shape on the tire circumference which in turn affects the contact patch shape have a significant influence to the tire performance during rotation.
In the following Patent Documents 1 to 3, for instance, a method is disclosed in which an acceleration sensor is attached to a tire to acquire measurement data of acceleration of the tire during rotation, and from the acquired measurement data, power spectrums and vibration spectrums are obtained to estimate the status of the road during the tire rotation, and also a method is disclosed in which a timing at which a tread portion is in contact with a road surface is determined from measurement data of acceleration in a radial direction.
However, in Patent Documents 1-3, while the status of the road surface can be estimated using the measurement data, it is impossible to calculate a deformation shape of a rotating tire or a dynamic contact length from the measurement data.    Patent Document 1: JP 2002-340863 A    Patent Document 2: JP 2003-182476 A    Patent Document 3: JP 2002-511812 A